There are a few primal sounds known to cause the heads of men to whirl and their eyes to alight with interest: the crack of bat on ball, the hiss of meat on flame and the simple, clarion shout of “Girl fight!”

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

Last Saturday night’s mixed martial arts bout between UFC women’s bantamweight champion Ronda Rousey and challenger Liz Carmouche – the first pay-per-view fight headlined by two women – attracted more than 15,000 fans to Anaheim’s Honda Center and the most media attention ever aimed at the Ultimate Fighting Championship, according to UFC president Dana White. Early estimates indicate that another 400,000-plus TV viewers anteed up 50 bucks to eyeball the battle.

But whether the female combatants are elite athletes, sitcom actorsor merely hostile office workers, not a lot of men are going to break up a female-versus-female throwdown anytime soon. Okay, at least not for a few minutes.

The question is, why?

“What kind of guys might be interested in watching women fighting?” muses Dr. Ronald Levant, professor of psychology at the University of Akron. “There might be a small group of men … interested because they believe women should have equal access to all sports – let’s call it the Title IX ethos.”

But the lion’s share of guys, he says, are probably interested in seeing women fight for more sexual reasons. As "Seinfeld" puts it in one episode, “Men think if women are grabbing and clawing at each other, there’s a chance they might somehow kiss.”

“For them, it is more of a prurient interest in seeing women trying to dominate each other,” says Levant. “They like seeing that kind of thing and are excited by that.”

Will Meek, a Portland, Ore., psychologist who specializes in the psychology of men, agrees.

“There are definitely men that sexualize what they are seeing – two women wearing little clothing having a close and intense physical encounter,” he says.

“People are interested in the novelty of women -- especially attractive women -- stepping outside of their own gender roles to fight each other,” says Meek. “Cage fighting with the intent to inflict serious harm on another person goes against most ways our culture imagines women to be, and thus creates a lot of curious interest.”